UNIVERSITY   OF   CALIFORNIA 

COLLEGE   OF   AGRICULTURE 

AGRICULTURAL   EXPERIMENT   STATION 

BERKELEY,    CALIFORNIA 


IRRIGATION  INVESTIGATIONS  WITH 

FIELD  CROPS  AT  DAVIS,  AND  AT 

DELHI,  CALIFORNIA 

1909-1925 

S.  H.  BECKETT  AND  M.  R.  HUBERTY 


(Based  on  data  gathered  in  cooperation  with  the  Division  of  Agricultural  Engineer- 
ing, Bureau  of  Public  Roads,  U.  S.  Department  of  Agriculture,  and  the  Division  of 
Engineering  and  Irrigation,  California  State  Department  of  Public  Works.) 


BULLETIN  450 

March,  1928 


UNIVERSITY  OF  CALIFORNIA  PRINTING  OFFICE 

BERKELEY,  CALIFORNIA 

1928 


IRRIGATION  INVESTIGATIONS  WITH  FIELD  CROPS 
AT  DAVIS,  AND  AT  DELHI,  CALIFORNIA,  1909-19251 

S.  H.  BECKETT2  and  MAETIN  E.  HUBEETY3 


This  bulletin  reports  the  results  of  certain  irrigation  experiments 
with  field  crops  in  the  Sacramento  and  San  Joaquin  valleys.  The 
work,  as  originally  planned,  was  limited  to  the  irrigation  tract  of  the 
University  Farm,  at  Davis,  the  purpose  being  to  determine  the  duty 
of  water  for  alfalfa  and  field  crops  and  the  methods  of  applying  the 
water  to  obtain  maximum  returns.  In  1922,  as  a  part  of  the  coopera- 
tive investigations,  alfalfa  studies  were  also  undertaken  on  the  irri- 
gation experimental  tract  at  Delhi,  in  the  San  Joaquin  Valley. 

INVESTIGATIONS   WITH    ALFALFA   AT  THE    UNIVERSITY    FARM 

AND   AT  DELHI 

In  1907,  a  tract  of  twenty-five  acres  was  set  aside.  Experiments 
were  started  in  1909.  The  planting  of  experimental  orchards  and 
vineyards  on  the  tract  in  1915  and  1917  necessitated  a  rearrangement 
of  the  fields,  making  it  impossible  to  maintain  a  uniform  system  of 
plot  numbering  throughout  the  sixteen  years  covered.  Figures  1  and  2 
show  the  general  arrangement  of  plots  during  the  periods  1911-1915 
and  1915-1925. 

The  soil  of  the  tract  is  described  as  a  Yolo  fine  sandy  loam  of 
medium  texture  to  a,  depth  of  18  to  20  feet,  having  a  maximum  soil 
moisture  'field  capacity '  of  20  to  22  per  cent.  At  no  time  during  the 
investigations  was  the  underground  water  table  closer  than  14  feet 
from  the  surface.  From  time  to  time,  attempts  were  made  to  obtain 
information  on  the  use  of  water  by  means  of  intensive  soil  sampling. 
Variability  of  the  soil  made  it  impossible,  however,  to  secure  reliable 
results  by  that  method.  The  experiments  were  limited,  therefore,  to 
a  study  of  yields  under  different  irrigation  treatments. 


i  Eesults  of  the  investigations  have  been,  in  part,  previously  published  in 
U.  S.  Department  of  Agriculture  Bulletin  10,  California  State  Department  of 
Engineering  Bulletin  3,  California  Agricultural  Experiment  Station  Bulletin 
280,  and  biennial  reports  of  the  State  Engineer  of  California  and  the  Director 
of  the  California  Agricultural  Experiment  Station. 

The  work  at  Davis  reported  herein  has  been  conducted  by  the  authors;  that 
at  Delhi  mainly  by  Martin  E.  Huberty  and  Frank  Davis,  Junior  Irrigation 
Engineer,  Division  of  Irrigation  Investigations  and  Practice. 

2  Associate  Professor  of  Irrigation  Investigations  and  Practice  and  Associate 
Irrigation  Engineer  in  the  Experiment  Station. 

3  Assistant  Irrigation  Engineer  in  the  Experiment  Station. 


4  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

The  water  supply  was  obtained  by  pumping,  a  storage  reservoir 
of  one-quarter  acre-foot  capacity  being  used  to  regulate  the  flow. 
Delivery  of  water  from  the  pump  and  the  reservoir  to  the  various 
field  ditches  and  plots  was  made  through  a  concrete  pipe  system. 

All  water  used  in  the  experiments  was  measured  by  means  either 
of  rectangular  weirs  located  in  weir  boxes  in  the  pipe  lines,  or  by 
temporary  weirs  installed  in  the  field  laterals. 


GOAD 


Fig.  1. — Experimental  irrigation  tract,  University  Farm,  Davis,  California, 
showing  areas  included  in  investigations,  1912-1915. 


Standard  practices  for  the  localities  were  followed  in  the  prepara- 
tion of  land  for  irrigation,  in  the  preparation  of  seed  bed,  and  in 
irrigation,  cultivation,  and  harvesting.  The  time  to  irrigate  was  deter- 
mined by  examination  of  the  moisture  condition  of  the  soil  and  by 
the  appearance  of  the  crop,  an  attempt  being  made  to  secure  maximum 
yields  under  the  various  treatments. 

In  1920,  a  tract  of  forty  acres  was  leased  from  the  State  Land 
Settlement  Board  at  Delhi,  California,  to  be  used  in  cooperative  irri- 


BUL.  450]  IRRIGATION  INVESTIGATIONS   WITH   FIELD   CROPS  5 

gation  investigations.  The  soil  of  the  tract  is  described  as  an  Oakley 
fine  sand,  ranging  in  depth  from  6  to  9  feet.  The  maximum  'field 
capacity'  ranges  from  6  per  cent  at  the  surface  to  10  per  cent  and 
12  per  cent  at  the  lower  depths.  A  tough  calcareous  hardpan,  light 
gray  in  color,  10  to  12  inches  in  thickness  and  practically  impervious 
to  water,  underlies  the  whole  area  at  depths  of  6  to  9  feet. 


/?OAD 


vN 


FIELD    1 

7.9  AC  PES 
/9I6    3EAHS 
/917'BO  ALFALFA 
/9EI  -as  F/ELD  CPOPS 


O/PCHAPD 
3.46  ACPES 


f/eld  a 

4.43  ACRES 
/9l6-'/9  F/ELO  CtfOPS 
/9aO-£5  ALFALFA 


F/ELD    4 
/.a  AC  PES 
/9/6-  'as  ALFALFA 


OPCHARD 


V/NFYA&D 


F/ELD  S 

/.  7S  ACPES 

19/6 -'SI     CPA/N 

/9aa-'a5  alfalfa 


r^  X — 7^ 

^cr^-^. \U  PUMP  MOUSE 


Fig.  2. — Experimental  irrigation  tract,  University  Farm,  Davis,  California, 
showing  areas  included  in  investigations,  1916-1925. 


Water  for  irrigation  was  obtained  by  pumping,  distribution  being 
made  to  the  entire  area  through  a  concrete  pipe  system.  Water  applied 
was  measured  by  rectangular  weirs  placed  in  the  distributing  system. 
Figure  3  shows  the  arrangement  of  the  plots  with  the  irrigation 
schedule  followed  from  1922  to  1925. 

The  land  was  prepared  for  irrigation  in  the  winter  of  1920  and 
seeded  to  alfalfa  in  the  spring  of  1921.  During  1921,  there  was  no 
variation  in  irrigation  treatment,  sufficient  water  being  applied  during 
the  season  to  produce  normal  growth. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


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Allotment     461 
Delhi 

3mTELAND<3teTTZEB!EM 

Used  for  cooperative 
irrigation  experiment 
with  a/fatfb 

Area  1 7  acres. 


Fig.  3. — Portion  of  irrigation  experimental  tract,  Delhi,  California, 
showing  arrangement  and  location  of  alfalfa  checks. 


Bul.  450] 


IRRIGATION   INVESTIGATIONS    WITH    FIELD    CROPS 


Irrigation  of  Alfalfa  at  Davis,  1910-1915,*  1918-1925;  and  at 
Delhi,  1922-1925. — The  treatments  in  the  irrigation  of  alfalfa  for  the 
periods  indicated  above  are  summarized  in  tables  1  and  2 ;  the  results 
of  the  experiments,  except  as  elsewhere  previously  reported,  are  given 
in  tables  3,  4,  and  5. 

TABLE   1 

Irrigation  Treatment  at  Davis 


Experiments  wii 

,h  various  depth 
1910-1915 

3  of  water  applied, 

Experiments  with  constant  depth  of  water  applied 
but  variable  number  of  irrigations,  1918-1925 

Number  of 
irrigations 

Unit  depth 

of  irrigation, 

inches 

Total  seasonal 

depth  water 
applied,  inches 

Number  of 
irrigations 

Unit  depth 

of  irrigation, 

inches 

Total  seasonal 

depth  water 
applied,  inches 

None 

2 

15 

30 

2 

6 

12 

3 

10 

30 

3 

6 

18 

4 

7H 

30 

4 

6 

24 

6 

5 

30 

4 

llA 

30 

8 

m 

30 

4 

9 

36 

12 

2V2 

30 

4 

12 

48 

4 

15 

60 

TABLE  2 
Irrigation  Treatment  at  Delhi 


Experiments  with  various  depths  of  water  applied, 
1922-1924 

Experiments  wi 
but  variable 

th  constant  depth  of  water  applied 
number  of  irrigations,  1922-1924 

Number  of 
irrigations 

Unit  depth 

of  irrigation, 

inches 

Total  seasonal 

depth  water 
applied,  inches 

Number  of 
irrigations 

Unit  depth 

of  irrigation, 

inches 

Total  seasonal 

depth  water 
applied,  inches 

3 

4 

12 

3 

12 

36 

3 

6 

18 

6 

6 

36 

4 

6 

24 

9 

4 

36 

5 

6 

30 

12 

3 

36 

6 

6 

36 

6 

7 

42 

6 

8 

48 

6 

10 

60 

Season  of  1925 


4  The  results  of  these  experiments  are  reported  in  detail  in:  Beckett,  S.  H., 
and  R.  D.  Robertson.  The  economical  irrigation  of  alfalfa  in  the  Sacramento 
Valley,  California.  Agr.  Exp.  Sta.  Bul.  2:80:271-294.  1917.  Adams,  Frank, 
et  al.  Investigations  of  the  economical  duty  of  water  for  alfalfa  in  Sacramento 
Valley,  California,  1910-1915.     State  Dept.  Engineering  Bul.  3:6-13.     1917. 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


TABLE  3 

Yields  of  Alfalfa  Plots  with  Seasonal  Depth  Constant  but  with  Varying 
Numbers  and  Depths  of  Irrigations,  Davis,  1918-1925 


Block 

Num- 
ber of 
plots 

Acre 

Number 

of 
irriga- 
tions 

Depth 

of  each 

irrigation, 

inches 

Total 

seasonal 

depth  of 

irrigation, 

inches 

Yield 

,  tons  to  the  acre 

Field 

1918 

1919 

1920 

1921 

Aver- 
age 

Avg. 

9yrs.* 

2 

3 

0.61 

2 

15 

30 

7.84 

9.66 

8.35 

6.64 

8.12 

8.24 

2 

3 

0.61 

3 

10 

30 

7.12 

10.60 

8.30 

8.22 

8.56 

8.41 

I 

2 

3 

0.61 

4 

7V2 

30 

7.28 

10.09 

6.88 

7.13 

7.85 

7.57 

2 

3 

0.61 

6 

5 

30 

8.00 

10.85 

7.48 

9.07 

8.85 

8.72 

3 

3 

0.59 

8 

m 

30 

8.90 

11.16 

8.07 

8.60 

9.18 

8.79 

3 

3 

0.54 

12 

2V2 

30 

10.21 

11.06 

9.09 

8.42 

9.70 

9.42 

1921 

1922 

1923 

1924 

1925 

Avg. 

2 

4 

0.68 

2 

15 

30 

8.25 

8.03 

7.80 

8.19 

9.36 

8.33 

2 

4 

0.68 

3 

10 

30 

7.70 

8.61 

8.50 

8.24 

8.42 

8.29 

II 

2 

4 

0.68 

4 

m 

30 

6.99 

7.22 

7.15 

7.36 

8.07 

7.36 

3 

4 

0.82 

6 

5 

30 

8.16 

7.92 

8.16 

9.15 

9.65 

8.61 

3 

4 

0.77 

8 

3M 

30 

8.43 

8.42 

8.42 

7.58 

9.49 

8.47 

3 

4 

0.71 

12 

2H 

30 

9.15 

9.75 

8.75 

8.55 

9.80 

9.20 

*  Average  of  four-year  trials  on  field  I  and  five-year  trials  on  field  II. 


TABLE  4 

Summary  of  Kesults  of  Alfalfa  Duty-of-Water  Experiments, 
Delhi,  California,  1922-1924 


Num- 

Acres 

Unit 
depth 
each  irri- 
gation, 
inches 

Total 
seasonal 

depth 
of  water 
applied, 

inches 

Yield,  tons  to  the  acre 

Average 
value 
of  hay 

per  acre* 

Average 

cost  of 

production 

per  acref 

Average 
profit 

ber  of 
plots 

1922 

1923 

1924 

Aver- 
age 

per  acre 

5 

0.875 

4 

12 

7.04 

4.98 

3.79 

5.27/ 

$58.00 

$24.08 

$33.92 

3 

0.475 

6 

18 

7.82 

5.23 

4.00 

5.68 

62.48 

27.22 

35.26 

5 

0.875 

6 

24 

8.60 

5.51 

4.63 

6.25 

68.75 

31.00 

37.75 

6 

1.040 

6 

30 

8.63 

6.37 

6.62 

7.21 

79.30 

36.34 

42.96 

6 

1.040 

6 

36 

9.23 

7.36 

8.02 

8.20 

90.20 

41.80 

48.40 

6 

1.040 

7 

42 

9.65 

8.07 

8.42 

8.71 

95.80 

45.34 

50.46 

6 

1.040 

8 

48 

8.95 

7.77 

8.53 

8.42 

92.60 

45.68 

46.92 

5 

0.875 

10 

60 

8.68 

7.46 

8.57 

8.24 

90.65 

47.96 

42.69 

Season  of  1925 


4  8 
5.2 
4.6 


6.63 
7.15 
6.45 


*  Figured  at  $11  a  ton  in  the  stack. 

t  Cost  of  water  figured  at  $1.50  an  acre-foot;  labor  of  irrigation  at  12}4  cents  an  acre-inch;  cntting, 
raking,  shocking,  and  handling  at  $4  a  ton. 


BUL.  450]  IRRIGATION   INVESTIGATIONS   WITH   FIELD   CROPS  9 

The  comparison  of  yields  under  varying  irrigation  treatments  at 
Davis  and  at  Delhi  is  made  graphically  in  figures  4  and  5. 


TABLE  5 

Yields  of  Alfalfa  Plots  with  Seasonal  Depth  Constant  but  with  Varying 
Numbers  and  Depths  of  Irrigations,  Delhi,  1922-1924 


Num- 
ber of 
(plots 

Acres 

Number 
of 
irriga- 
tions 

Depth 

of  each 

irrigation, 

inches 

Total 

depth  of 

irrigation, 

inches 

Yield,  tons  to  the  acre 

1922 

1923 

1924 

Average 

6 

1  07 

3 

12 

36 

7.29 

7.00 

6.05 

6.78 

6 

1  07 

6 

6 

36 

7.89 

7.00 

6.85 

7.25 

6 

1.07 

9 

4 

36 

7.70 

7.40 

7.46 

7.52 

6 

1  07 

12 

3 

36 

7.06 

6.69 

7.57 

7.11 

The  Effect  of  the  Amount  and  Frequency  of  Irrigation  on  the 
Root  Development  of  Alfalfa. — At  the  conclusion  of  the  experiments 
at  Davis  and  at  Delhi,  in  which  a  constant  seasonal  depth  of  water 
had  been  applied  in  varying  amounts  and  frequencies  of  time,  obser- 
vations were  made  to  determine  the  effect  of  these  treatments  on  the 
root  development  of  the  alfalfa. 

At  a  point  near  the  center  of  a  representative  plot  of  each  treat- 
ment, an  area  3  by  5  feet  was  selected  under  conditions  of  uniform 
stand  and  where  examination  showed  the  soil  to  be  of  uniform  type. 

A  templet  with  inside  dimensions  of  3  by  5  feet  was  fastened  to 
the  ground  surface.  All  plants  within  this  area  were  trimmed  to  a 
stem  length  of  one  inch  above  the  crown,  the  number  of  plants  then 
counted,  and  cut  off  at  a  point  immediately  below  the  crown. 

It  wras  originally  planned  to  remove  the  soil  in  layers  and  by  wash- 
ing through  screens,  to  separate  the  roots  so  their  weights  could  be 
obtained.  It  wTas  found,  however,  that  the  gravel  contained  in  the  soil 
fouled  the  finer  screens  to  such  an  extent  that  no  progress  could  be 
made.  The  dry  soil  was  therefore  removed,  pulverized  and  then  passed 
through  a  % -inch-mesh  screen,  and  the  roots  separated  by  hand. 

Tables  6  and  7  show  the  dry  weights  of  roots  obtained  and  their 
distribution  in  percentage  of  total  weight  taken  from  a  6-foot  depth. 

Figures  6  and  7  show  the  root  distribution  under  varying  irri- 
gation treatments  at  Davis  and  Delhi. 


TABLE  6 
Root  Distribution  under  Varying  Irrigation  Treatments  at  Davis 


Twelve 

2^-inch 
irrigations 

Eight 

3%-inch 

irrigations 

Six  5-inch 
irrigations 

Four 

7^-inch 

irrigations 

Three 

10-inch 

irrigations 

Two  15-inch 
irrigations 

Depth,  inches 

Dry 

wt., 
grams 

Per 
cent 

of 
total 

Dry 

wt., 
grams 

Per 
cent 

of 
total 

Dry 

wt., 

grams 

Per 

cent 

of 
total 

Dry 

wt., 
grams 

Per 

cent 

of 
total 

Dry 

wt., 
grams 

Per 
cent 

of 
total 

Dry 

wt., 
grams 

Per 
cent 

of 
total 

390.7 
238.4 
102.6 
86.6 
61.7 
54.2 
45.8 
34.8 
28.1 
22.4 
19.2 
17.2 
11.8 

460.1 
338.0 
121.8 
81.1 
64.3 
42.0 
38.4 
31.1 
18.1 
19.9 
17.3 
14.4 
12.2 

407.6 

340.7 

146.0 

115.5 

62.0 

63.0 

44.4 

40.0 

27.3 

24.3 

21.3 

15.9 

15.3 

410.0 
256.6 
113.0 
86.5 
63.0 
53.3 
41.9 
37.2 
30.3 
25.3 
25.1 
19.0 
20.2 

577.8 
290.0 
157.6 
88.2 
73.2 
52.7 
50.9 
35.4 
26.2 
26.4 
20.1 
15.5 
17.2 

415.9 

342.3 

149.7 

112.7 

78.4 

48.4 

41.6 

34.2 

41.8 

29.0 

32.0 

26.3 

21.5 

0-  6 

33.0 
14.2 
11.9 
8.5 
7.5 
6.3 
4.8 
3.9 
3.1 
2.7 
2.4 
1.6 

42.3 
15.2 
10.1 
8.1 
5.3 
4.8 
3.9 
2.3 
2.5 
2.2 
1.8 
1.5 

37.2 
15.9 
12.6 
6.8 
6.9 
4.8 
4.4 
3.0 
2.6 
2.3 
1.8 
1.7 

33.2 
14.6 
11.2 
8.2 
7.0 
5.4 
4.8 
3.9 
3.3 
3.3 
2.5 
2.6 

34.0 
18.5 
10.3 
8.6 
6.2 
6.0 
4.1 
3.0 
3.1 
2.4 
1.8 
2.0 

35.7 

6-12 

15.6 

12-18 

11.8 

18-24 

8.2 

24-30 i 

5.0 

30-36 

4.3 

36^12 

3.6 

42-18 

4.4 

48-54 

3.1 

54-60 

3.3 

60-66 

2.8 

66-72 

2.2 

10 
§9 

k 

£>  7 

i 

*, 

J2  13  24  JO  36  48 

DEPTH   OF  I RR I  GAT/ON  IN  INCHES 


60 


Fig.  4. — Diagram  showing  results  of  alfalfa  duty-of-water  experiments  at 
University  Farm,  Davis,  1910-1915.  Note  the  maximum  yield  with  an  annual 
application  of  36  inches  of  water.  Under  the  conditions  present,  the  most 
economical  yields  were  obtained  with  annual  applications  of  30  to  36  inches. 


TABLE  7 

Boot  Distribution  of  Alfalfa  under  Variable  Irrigation  Treatments 

at  Delhi 


Depths, 

inches 

Six  8-inch  irriga- 
tions, 1922-25 

Six  6-inch  irriga- 
tions, 1922-25 

Three  4-inch 
irrigations,  1922-24; 
six  6-inch  irriga- 
tions, 1925 

Twelve  3-inch 
irrigations,  1922-24; 
four  6-inch  irriga- 
tions, 1925 

Dry  wt., 
grams 

Per  cent 
of  total 

Dry  wt., 
grams 

Per  cent 
of  total 

Dry  wt., 
grams 

Per  cent 
of  total 

Dry  wt., 

grams 

Per  cent 
of  total 

305.8 
396.4 
201.7 
135.9 
103.4 

62.8 

44.3 

29.1 

18.3 

12  1 

8.8 

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371.4 

451.7 

228.3 

140.0 

112.6 

89.7 

66.7 

41.1 

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es      8.7 

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1.8 
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11.6 

18-24 

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6.0 

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5.8 

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3.7 

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Fig.  5. — Diagram  showing  results  of  alfalfa  duty-of -water  experiments  at 
Delhi,  California,  1922-1924.  Note  the  maximum  yields  with  an  annual  appli- 
cation of  42  inches  of  water.  Under  the  conditions  present,  the  most  economical 
yields  were  obtained  with  annual  applications  of  36  to  42  inches. 


12 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


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Fig.  6. — Diagram  showing  root  distribution  of  alfalfa  under  varying  irri- 
gation treatments  at  University  Farm,  Davis.  Note  that  the  root  distribution 
has  apparently  not  been  affected  by  variation  in  irrigation  treatments. 


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14  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Conclusions  on  Irrigation  of  Alfalfa  at  Davis  and  Delhi. 

1.  At  Davis,  the  average  maximum  yield  and  the  average  maxi- 
mum profit  were  produced  with  total  seasonal  applications  of  36  acre- 
inches  to  the  acre,  but  the  difference  between  the  yields  produced  by 
30  inches  and  those  produced  by  36  inches  is  so  slight  that  it  is  not 
significant;  30  acre-inches  per  acre,  therefore,  can  be  considered  an 
economic  seasonal  application  under  the  conditions  present, 

2.  Total  depths  of  less  than  24  inches  annually,  exclusive  of  rain- 
fall, are  insufficient  for  satisfactory  yields.  Applications  of  depths 
of  48  inches  or  more  annually  produce  smaller  yields  than  were 
obtained  by  applying  36  inches. 

3.  Variation  in  the  number  of  irrigations  (three  to  twelve),  when 
a  total  seasonal  depth  of  30  inches  was  applied,  caused  only  small 
differences  in  yield.  The  lighter  applications  given  at  more  frequent 
intervals  tended  to  produce  the  higher  yields,  but  the  increases  in 
yields  did  not  warrant  the  extra  labor  cost  and  the  inconvenience  of 
applying  frequent  light  irrigations.  In  loam  soils,  under  Sacramento 
Valley  conditions,  a  total  seasonal  application  of  30  inches  applied  in 
four  irrigations  represents  good  irrigation  practice  for  alfalfa.  Obser- 
vations in  other  localities  have  shown  that  the  very  open  or  very 
impervious  soils  should  be  irrigated  more  than  once  between  cuttings. 

4.  At  Delhi,  the  maximum  yields  were  produced  by  42  acre-inches 
of  water  to  the  acre,  or  by  six  inches  more  than  was  required  at 
Davis — an  amount  about  equal  to  the  difference  in  rainfall  between 
the  two  stations. 

5.  Even  in  the  light  soil  at  Delhi,  variations  in  number  of  irri- 
gations, providing  the  same  seasonal  total  was  applied,  did  not  materi- 
ally affect  the  yield.  No  doubt  the  impervious  layer  at  a  depth  of 
about  six  feet  prevented  the  loss  of  a.  large  part  of  the  water  applied 
in  the  heavy  irrigations,  this  water  being  used  by  the  crop  in  the 
interval  between  irrigations. 

6.  Under  field  conditions,  both  at  Davis  and  at  Delhi,  during  a 
period  when  the  winter  rainfall  was  sufficient  to  moisten  the  soil  to 
a  depth  of  at  least  six  feet,  and  where  the  depth  to  the  underground 
water  table  was  more  than  15  feet,  variation  in  depth  of  application 
or  in  frequency  of  irrigation  did  not  affect  the  root  distribution  of 
the  alfalfa. 

7.  On  the  average,  at  Davis,  52  per  cent  of  the  roots  by  weight 
were  found  in  the  top  foot  and  71  per  cent  in  the  top  two  feet  of  soil. 
At  Delhi,  the  top  foot  contained  56  per  cent  of  the  roots  and  the  top 
two  feet  78  per  cent.    Only  the  top  six  feet  of  soil  was  considered. 


Bul.  450] 


IRRIGATION   INVESTIGATIONS   WITH    FIELD    CROPS 


15 


INVESTIGATIONS  OF   MISCELLANEOUS   FIELD   CROPS  AT   DAVIS, 

1910-1925 

From  1912  to  1915,  a  crop  rotation  plan  was  outlined  for  blocks 
1  to  6,  shown  in  figure  1.     This  plan  is  shown  in  the  following  table. 

TABLE  8 
Rotation  Plan  of  Field  Irrigation  Experiments  at  Davis,  1912-1915 


Area, 
acres 

Crop 

Block 

1912 

1913 

1914 

1915 

j 

1.79 
1.89 
1.84 
2.33 
2.64 
1.55 

2 

3 

Grain(barley  and  wheat) 

4 

Grain  (wheat  and  oats).. 

5 

Grain  (barley) 

6 

The  cropping  followed  from  1916  to  1925  is  shown  in  figure  2. 

Irrigation  of  Wheat,  Oats,  and  Barley. — These  investigations 
covered  a  period  of  eleven  years,  beginning  in  1910  and  terminating 
in  1921.  From  1912  to  1915,  the  trials  were  carried  on  as  a  part  of 
the  crop-rotation  scheme  covering  a  period  of  the  four  years  outlined 
above. 

It  was  intended  that  the  work  with  wheat  and  oats  should  extend 
over  a  longer  period  than  was  covered.  It  was  found,  however,  that  a 


TABLE  9 

Period  Covered  by  the  Grain  Investigation  and  the  General  Plan  of 

Irrigation  Treatment 


Crop 

Year 

Irrigation  treatment 

Remarks 

Barley 

1910-1916 

One,  two,  or  three  spring  irrigations  applied 
as  indicated  by  crop  needs. 

1910-1911  on  old  grain  land,  1912-1916 
a  part  of  rotation  scheme  of  field 
crops  following  alfalfa. 

Barley 

1913-1921 

Summer  and  fall  irrigation  before  seeding. 
Each  year  plot  1  received  no  irrigation, 
plot  2  was  thoroughly  irrigated  immedi- 
ately after  harvest  and  fallowed,  plot  3  was 
irrigated  each  year  prior  to  fall  seeding. 

1913-1921  cropped  continuously  to 
barley  on  land  on  which  only  grain 
had  previously  been  raised. 

Wheat 

1912-1914 

One  or  two  spring  irrigations  applied  accord- 
ing to  crop  needs. 

As  a  part  of  the  rotation  of  field  crops 
following  alfalfa. 

Oats 

1912-1913 

One  or  two  spring  irrigations  applied  accord- 
ing to  crop  needs. 

As  a  part  of  the  rotation  of  field  crops 
following  alfalfa. 

TABLE  10 
Kesults  of  Spring  Irrigation  of  Barley,  1910-1916  (at  Davis) 


Season 

Seasonal 
rainfall, 

inches 

Plot 

Area, 
acres 

Number  of 
irrigations 

Depth 
of  water 
applied, 

inches 

Yield 
grain, 
pounds 
per  acre 

Ratio 
grain  to 

straw 

Cost  of 

irrigation, 

per  acre 

Crop 

of  previous 

year 

11.90 

6A 
6B 
6C 

1.25 
0.50 
0.50 

0 

1 
2 

1,160* 
1,480* 
1,840* 

1:1.70 
1:1.32 
1:1.86 

Barley 
Barley 
Barley 

1910 

3.6 

6.2 

$1.08 
1.86 

23.18 

6A 
6B 
1  A 
IB 
1C 

0.72 
0.67 
0.50 
0.50 
0.50 

0 

1  (late) 

1  (early) 

1  (early) 

2 

850* 
1,515* 
1,108 
2,146 
1,810* 

1:0.82 
1:0.79 
1:0.84 
1:0.75 
1:0.76 

Barley 
Barley 
Barley 
Cow  peas 
Barley 

1911 

5.6 
4.3 
6.0 
7.0 

$1.68 
1.29 
1.80 
2.10 

9.46 

6A 
3  A 
3B 
3C 

1.48 
0.49 
0.48 
0.49 

0 
0 
1 
2 

346 
1,040* 
1,285* 
1,950* 

1:0.95 
1:0.89 
1:1  15 
1:0.94 

1912 

Alfalfa 

7.4 
16.9 

$2.22 
5  07 

Alfalfa 
Alfalfa 

8.74 

6A 
7A 
7B 
7C 

1.10 
0.25 
0.25 
0.25 

0 
0 
1 

2 

448 
320* 
2,144* 
2,556* 

1:0.95 
1:2.75 
1:1.50 
1:2.60 

Barley 

1913 

9.2 
13  4 

$2.76 
4.02 

Corn 
Corn 

28.70 

6  A 
5  A 
5B 
5C 
5D 

1.20 
0.57 
0.19 
0.19 
0.19 

0 
0 
1 
1 
1 

1,790 
2,070* 
1,955 
2,535* 

2,695 

1:1.08 
1:1.20 
1:2.38 
1:1.50 
1:1.30 

Barley 

1914 

4  0 
8.0 
12  0 

$1.20 
2.40 
3.60 

Potatoes 
Potatoes 
Potatoes 

20.05 

6A 
1  A 
IB 
1C 
1  D 
IE 

0  51 
0.26 
0.25 
0.25 
0.25 
0.25 

0 
0 

1 
1 

1 
1 

1,325 

1,970* 

2,085 

2,085 

2,165* 

2,210 

1:1.81 
1:1.43 

1:1.28 
1:1.39 
1:1.29 
1:1.20 

Barley 

1915 

3.0 
4.5 
6.0 

7.5 

$0.90 
1.35 
1.80 
2.25 

Sugar  beets 
Sugar  beets 
Sugar  beets 
Sugar  beets 

1916 

20.88 

2A 
2A 

3.90 
4.00 

0 

1 

1,188* 
1,460* 

1:2.90 
1:3.00 

Barley 
Barley 

3.2 

$0.96 

Yields  used  in  preparing  table  11. 

TABLE  11 

Comparison  of  Yields  After  Seasons  of  Light  and  Heavy  Eainfall 

(at  Davis) 


Seasons 

Average 
seasonal 
rainfall, 

inches 

Number 
of  irriga- 
tions 

Average 

depth  of 

water  applied, 

inches 

Average 

yield*  of 

grain,  lbs. 

per  acre 

Ratio 

grain  to 

straw 

Cost  of 
irrigation 
per  acre 

1910,  1912, 

10.07 

0 

1 
2 

6.7 
12.2 

840 
1,636 
2,115 

1:1.78 
1:1.32 
1:1.80 

1913 

$2.02 
3.65 

1911,  1914, 

23.20 

0 
1 
2 

5.2 
7.0 

1,520 
1,780 
1,810 

1:1.58 
1:1.72 
1:0.76 

1915,  1916 

$1.56 
2.10 

*  In  preparing  table  11,  yields  marked  with  an  asterisk  (*)  in  table  10  were  used.  Results  obtained 
from  plot  6  A  in  1912-1915  were  eliminated,  since  a  fair  comparison  could  not  be  made  between  an  unirri- 
gated  area  continuously  planted  to  barley  and  an  unirrigated  area  under  crop  rotation. 


TABLE  12 

Results  of  Irrigation  of  Barley  Land  Before  Seeding,  1913-1921  (at  Davis) 


Season 

Seasonal 

rainfall, 

inches 

Irrigation  treatment 

Depth 

water 

applied, 

inches 

Yield 
grain, 
pounds 
per  acre 

Ratio 

grain  to 

straw 

Cost  of 
irriga- 
tion 

1913 

8.84 

438 
3,306 

1:0.99 
1:1.25 

One  fall  irrigation  before  seeding 

12.0 

$3.60* 

28.70 

1,790 
2,000 

1:1.08 
1:1.11 

1914 

10.0 

$3.00 

20.05 

1,325 
1,330 
1,460 

1:1.81 
1:1.75 

1:2.09 

1915 

9.0 
9.0 

$2  70 

One  summer  irrigation  before  seeding .... 

2.70 

20.88 

1,280 
1,555 
1,555 

1:1.13 
1:1.50 
1:1.16 

1916 

10.3 
10.3 

$3  09 

One  summer  irrigation  before  seeding  ... 

3.09 

14.11 

2,505 
2,311 

2,258 

1:0.81 
1:0.99 
1:1.33 

1917 

11.3 
11.3 

$3  39 

One  summer  irrigation  before  seeding  ... 

3.39 

9.66 

714 
1,595 
1,515 

1:1.67 
1:1.74 
1:2.56 

1918 

9.2 
9.2 

$2  80 

One  summer  irrigation  before  seeding  ... 

2.80 

19.40 

2,285 
1,330 
1,913 

1919 

One  fall  irrigation  before  seeding 

One  summer  irrigation  before  seeding  ... 

10.7 
10.7 

$3  21 

3  21 

8.94 

202 
1,332 
1,702 

1:2.32 
1:2.00 
1:1.75 

1920 

One  fall  irrigation  before  seeding 

One  summer  irrigation  before  seeding .... 

10.2 
10.2 

$3.06 
3.06 

16.92 

Nonef 

2,483 

2,935 

1921 

11.2 
11.2 

$3  06 

One  summer  irrigation  before  seeding .... 

3  06 

*  Cost  of  irrigation  (water  and  labor)  figured  at  30  cents  per  acre-inch. 

t  Climatic  conditions  did  not  permit  seeding  until  Feb.  11,  and  crop  did  not  reach  sufficient  height 
to  be  harvested. 

TABLE  13 

Comparison  of  Yields  of  Barley  After  Seasons  of  Light  and  Heavy 

Rainfall  (at  Davis) 


Seasons 

Average 

seasonal 

rainfall, 

inches 

Irrigation  treatment 

Depth 

water 

applied, 

inches 

Yield 
grain, 
pounds 
per  acre 

Ratio 

grain  to 

straw 

1913,  1917, 

11.69 

772 
2,205 
2,102 

1-1  45 

1918,  1920, 

10.8 
10.8 

1-1  50 

1921 

1*1  88 

1914,  1915, 

22.26 

1,670 
1,554 
1,643 

1-1  23 

1916,  1919 

10.5 
10.5 

1*1  45 

1:1.62 

All  years 
1913-1-921 

16.35 

1,171 
1,916 
1,905 

1:1.36 
1:1.48 
1:1.78 

10.6 
10.6 

18 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


very  appreciable  portion  was  shattered  each  year  during  heavy  north 
winds,  making  it  impossible  to  obtain  a  true  measure  of  the  yields, 
when  the  crops  were  allowed  to  ripen.  The  plan  of  the  experiments 
is  outlined  in  table  9.  Tables  10  to  15  give  the  data  obtained.  A 
comparison  of  the  yields  with  the  corresponding  depths  of  water 
applied  is  made  in  figure  8. 

TABLE   14 
Results  of  Spring  Irrigation  of  Wheat,  1912-1914  (at  Davis) 


Season 

Seasonal 

rainfall, 

inches 

Plot 

Number 
of  irriga- 
tions 

Depth  of 

water  applied, 

inches 

Yield  grain, 
pounds 
per  acre 

Ratio 

grain  to 

straw 

Cost  of 
irrigation* 

0 

0 

564 

1:2.10 

1912 

9.46 

1 

1 

10.0 

1,210 

1:2.25 

$3.00 

2 

2 

17.6 

1,930 

1:2.26 

5.28 

0 

1 

0 
1 

2.0 

127 

566 

1:3.89 
1:5.50 

$0.60 

2 

1 

4.0 

1,315 

1:2.33 

1.20 

3 

2 

6.0 

1,605 

1:3.15 

1.80 

4 

2 

8.0 

1,632 

1:3.00 

2.40 

1913 

8.74 

5 

2 

10.0 

1,792 

1:3.12 

3.00 

6 

2 

12.0 

1,610 

1:2.90 

3.60 

7 

2 

15  0 

1,240 

1:3.64 

4.50 

iot 

lit 

0 

1,354 

1:1.72 

1 

6.8 

1,730 

1:1.92 

2.04 

12t 

2 

13.0 

1,872 

1:2.22 

3.90 

0 
1 

0 
1 

4.0 

1,225 

946 

1:3.70 
1:3.71 

$1.20 

1914 

28.70 

2 

1 

8.0 

913 

1:4.55 

2.40 

3 

2 

12.0 

853 

1:4.61 

3.60 

4 

2 

16.0 

818 

1:4.20 

4.80 

5 

2 

20.0 

776 

1:4.14 

6.00 

*kCost  of  irrigation  (water  and  labor)  figured  at  30  cents  per  acre-inch. 
t  In  cow  peas,  season  1912. 


TABLE  15 
Results  of  Spring  Irrigation  of  Oats,  1912-1913  (at  Davis) 


Season 

Seasonal 

rainfall, 

inches 

Plot 

Number 
of  irriga- 
tions 

Depth  of 

water  applied, 

inches 

Yield  grain, 
pounds 
per  acre 

Ratio 

grain  to 

straw 

Cost  of 
irrigation* 

1912 

9.46 

0 

1 
2 

0 
1 
2 

13.2 
21.8 

437 
1,470 
2,050 

1:2.25 
1:2.32 
1:1.84 

$3.96 
6.54 

1913 

8.74 

0 
1 

2 

0 

1 
2 

8.1 
15.8 

0 
1,016 
1,508 

0 
1:3.86 
1:4.33 

$2.43 
4.74 

*  Cost  of  irrigation  (water  and  labor)  figured  at  30  cents  per  acre-inch. 


BUL.  450]  IRRIGATION  INVESTIGATIONS   WITH   FIELD   CROPS 


19 


eaoo 

2000 


1800 


Uiree  Y^ars-  Average 
Seasonal  Painfoli  10.07 in. 


/600 
q.  ^/400 

^k^/ooo 
^  %soo 
ilooo 


Four  Yeorsj  Average 
5eosona/  Rainfall  £3.3  in. 


% 

i 


400 

eoo 
o 
e 

6 
S 
10 
12 


a  o 

Number    of  Irrigations 


Fig.  8. — Diagram  showing  results  of  spring  irrigation  of  barley  at  University 
Farm,  Davis,  1910-1916.  Note  the  heavy  increase  in  yield  due  to  irrigation  in 
dry  years  and  the  comparatively  low  increases  in  years  of  heavy  rainfall. 


Conclusions  on  Irrigation  of  Grain. 

1.  Under  Sacramento  Valley  conditions,  with  a  seasonal  rainfall  of 
17  inches  or  more,  normally  distributed,  the  increase  in  grain  yields 
do  not  warrant  irrigation. 

2.  In  years  of  deficient  rainfall,  normal  yields  of  grain  may  be 
produced  with  irrigation.     The  number  of  irrigations  and  depth  of 


20  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

water  which  should  be  applied  in  years  of  deficient  rainfall  depends 
upon  the  rainfall  and  its  distribution,  and  general  weather  conditions 
during  the  growth  of  the  crop. 

3.  Under  conditions  of  extreme  rainfall  deficiency,  such  as  1910, 
1912,  and  1913,  two  irrigations  of  four  to  six  acre-inches  to  the  acre 
should  be  sufficient  to  produce  normal  yields.  Under  conditions  of 
partial  drought,  especially  where  a  deficiency  of  rainfall  occurs  in  the 
late  winter  and  early  spring  (March  and  April),  satisfactory  yields 
may  be  obtained  through  one  irrigation. 

4.  In  years  of  heavy  rainfall,  irrigation  may  produce  a  decrease  in 
yield.  However,  if  this  rainfall  should  be  unequally  distributed, 
with  a  deficiency  during  March  and  April,  irrigation  water  may  be 
applied  with  advantage. 

5.  Irrigation  of  grain  land  before  seeding  (either  in  the  summer 
or  in  the  fall  just  prior  to  seeding)  produces  no  increase  in  yields  in 
years  of  normal  rainfall.  In  years  of  deficient  rainfall,  normal  yields 
will  be  produced  by  this  method  of  irrigation.  In  years  of  drought 
the  average  yield  produced  by  this  method  was  one-third  greater  than 
the  average  yields  produced  in  years  of  normal  rainfall. 

6.  According  to  the  results  obtained  in  the  eight  years  covered  by 
these  experiments,  there  have  been  six  years  out  of  the  past  eighteen 
years  (1909-1926),  at  the  University  Farm,  Davis,  when  irrigation 
would  probably  have  produced  no  material  increase  in  yields;  six 
years  in  which  the  distribution  and  amount  of  rainfall  was  such  that 
one  spring  irrigation  could  have  been  applied  with  advantage;  and 
six  years  in  which  two  irrigations  would  have  been  required  for  full 
production. 

Irrigation  of  Corn  and  Grain  Sorghum,  1910-1922  (at  Davis). — 
Investigations  with  these  crops  were  started  in  1910  and  continued 
through  1915.  In  1922,  the  work  was  started  again  on  another  tract 
of  the  University  Farm,  but  a  readjustment  of  experimental  areas 
forced  a  temporary  discontinuation  at  the  end  of  that  season. 

In  the  production  of  corn  and  grain  sorghum,  standard  practices 
in  the  preparation  of  seed  bed,  seeding,  cultivation,  and  harvesting 
were  followed,  the  only  variable  factors  being  the  frequency  of  irri- 
gation and  depths  of  water  applied.  In  irrigation,  the  furrow  method 
was  used.  A  thorough  cultivation  followed  each  application  of  water. 
The  water  applied  was  measured  by  temporary  weirs  installed  in  the 
field  laterals. 


&s 


Depth    of  /rr/'gat/on  Y/e/o*    of    Ehs/fcrge 

/'n    inches  in   tons  per  acre 


22 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT   STATION 


The  results  of  yields  under  varying  irrigation  treatment  in  years 
of  light,  average,  and  heavy  rainfall  are  shown  in  figure  9. 


TABLE  16 

Eesults  of  Irrigation  of  Indian  Corn,  1910-1915  and  1922  (at  Davis) 


Season 

Seasonal 
rainfall, 

inches 

Plot 

Area 

of  plot, 

acres 

Number 

of 
irriga- 
tions 

Depth 

water 

applied, 

inches 

Yield 

of  ensilage 

tons 

per  acre 

Cost 
irriga- 
tion* 

Crop  of 
previous  years 

0 

0.67 

0 

6.91 

1910 

11.90 

1 

0.32 

1 

3.3 

8.84 

$1.82 

1908,  barley 

2 

0.32 

2 

5.3 

10.00 

3.12 

1909,  sugar  beets 

3 

0.67 

3 

8.0 

10.50 

4.70 

0 

0.54 

0 

3.67 

1908,  barley 

1911 

23.18 

1 

0.54 

1 

2.3 

4.86 

$142 

1909,  sugar  beets 

2 

0.54 

2 

4.7 

5.22 

2.88 

1910,  Indian  corn 

3 

0.54 

3 

7.1 

6.88 

4.34 

0 

0.31 

0 

3.66 

1912 

9.46 

1 

0.35 

1 

4.0 

4.57 

$2.10 

1909-1911,  alfalfa 

2 

0.35 

2 

8.6 

5.81 

4.42 

3 

0.35 

3 

14.6 

6.60 

7.32 

0 

0.26 

0 

1.54 

1 

0.26 

1 

3.0 

3.80 

$1.70 

1913 

8.74 

2 

0.26 

2 

6.0 

3.36 

3.40 

1909-1911,  alfalfa 

3 

0.26 

3 

9.0 

4.99 

5.10 

1912,  potatoes 

4 

0.26 

4 

12.0 

6.74 

6.80 

5 

0.26 

5 

15.0 

7.05 

8.50 

0 

0.27 

0 

3.93 

1 

0.27 

1 

4.0 

7.38 

$2.10 

2 

0.27 

2 

8.0 

11.48 

4.20 

1909-1911,  alfalfa 

1914 

28.70 

3 

0.27 

3 

12.0 

12.02 

6.30 

1912,  oats 

4 

0.27 

4 

16.0 

11.65 

8.40 

1913,  sugar  beets 

5 

0.27 

4 

19.2 

11.70 

9.68 

6 

027 

4 

23.2 

11.83 

11.28 

0 

0.63 

0 

4.02 

1909-1911,  alfalfa 

1915 

20.05 

1 

0.56 

1 

4.0 

9.87 

$2.10 

1912,  sugar  beets 

2 

0.59 

2 

8.0 

12.22 

4.20 

1913,  wheat 

3 

0  54 

3 

12.0 

14.15 

6.30 

1914,  potatoes 

50,  51,  52, 

0.38 

0 

4.00 

47,  48,  49, 

0.38 

1 

3.0 

4.96 

$1.90 

1913-1917,  alfalfa 

1922 

16.62 

44,  45,  46, 

0.38 

2 

5.8 

6.92 

3.32 

1918,  barley 

19,  20,  43, 

0.38 

3 

11.3 

8.35 

4.84 

1919-1921,  corn 

16, 17, 18. 

0.37 

4 

15.7 

8.16 

8.28 

*  Cost  of  irrigation  (water  and  labor)  figured  at  40  cents  per  acre-inch;  irrigation  furrowing  at  50  cents 
per  acre  per  irrigation. 


BUL.  450]  IRRIGATION  INVESTIGATIONS   WITH   FIELD   CROPS 


23 


TABLE  17 

Summary  and  Comparisons  of  Yields,  Indian  Corn  (Ensilage)  Following 
Seasons  of  Light  and  Heavy  Eainfall  (at  Davis) 


Years 

Average  sea- 
sonal rainfall, 
inches 

Number 

of 
irrigations 

Depth  water 

applied, 

inches 

.....                 v 

Yields, 

tons  per 

acre 

Cost  of 
irrigation 
per  acre* 

1910,  1912,  1913  (dry  years) 

9.97 

0 

2 
3 

3.4 
6.6 
10.5 

4.04 
5.73 
6.40 

7.36 

SI.  86 

3.64 
5.70 

1911, 1914, 1915, 1922  (wet  years) 

22.14 

0 
1 

2 
3 
4 

3.6 

6.8 

10.6 

15.8 

3.91 
6.77 
8.96 
10.35 
9.90f 

$1.94 
3.72 
5.74 
8.32 

1910-1915,  1922 

16.95 

0 

2 
3 
4 

3.5 
6.7 
10.6 
14.6 

3.98 
6.33 
7.86 
9.07 
8.851 

$1.90 
3.68 

5.74 

7.84 

*  Cost  of  irrigation  (water  and  labor)  figured  at  40  cents  per  acre-inch;  irrigation  furrowing  at  50  cents 
per  acre  per  irrigation. 

t  Average  of  2  years  only  (1914,  1922).  %  Average  of  3  years  only  (1913,  1914,  1922). 


TABLE  18 

Eesults  of  Irrigation  of  Dwarf  Milo  Maize,  1910,  1911,  1913,  and  1922 

(at  Davis) 


Season 

Seasonal 

Rainfall, 

inches 

Plot 

Area 

of  plot, 

acres 

Number 

of 
irriga- 
tions 

Depth 
of  water 
applied, 

inches 

Yield 
of  grain, 
pounds 
per  acre 

Cost  of 
irriga- 
tion* 

Crop  of 

previous  years 

1910 

11.90 

0 
1 
2 

0.30 
0.30 
0.30 

0 
1 
2 

3.8 
5.5 

1,340 
2,680 
2,710 

$2.02 
3.20 

1908,  barley 

1909,  sugar  beets 

1911 

23.18 

0 

1 
2 
3 

0.54 
0.54 
0.54 
0.54 

0 

1 
2 
3 

1.8 
4.6 
5.6 

1,018 
1,565 
2,453 
2,530 

$1.22 
2.84 
3.74 

1908,  barley 

1909,  sugar  beets 

1910,  dwarf  milo 

1913 

8.74 

0 
1 
2 
3 
4 
5 
6 

0.26 
0.26 
0.26 
0.26 
0.26 
0.26 
0.26 

0 

2 
3 
4 
5 
6 

3.0 
6.0 
9.0 
12.0 
15.0 
18.0 

230 

614 

998 

1,074 

1,343 

1,842 

$1.70 
3.40 
5.10 
6.80 
8.50 

10.20 

1909,  1911,  alfalfa 
1912,  barley 

1922 

16.63 

74,  75,  76, 
77,  78,  79, 
80,81,82, 
83,  87,  84, 
85,  86. 

0.25 
0.36 
0.37 
0.37 
0.37 

0 
1 
2 
3 
4 

3.4 
7.1 
11.1 
13.6 

3,835 
4,295 
5,187 
5,152 
5,747 

$1.86 
3.84 
5.94 
7.44 

1913-1917,  alfalfa 
1918,  barley 
1919-1921,  corn 

*  Cost  of  irrigation  (water  and  labor)  figured  at  40  cents  per  acre-inch ;  irrigation  furrowing  at  50  cents 
per  acre  per  irrigation. 


24 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


TABLE  19 

SUMMARY   OF   IRRIGATION  OF   DWARF  MlLO   MAIZE,    1910-1911,   1913,   AND   1922 


Years 

Average  sea- 
sonal rainfall, 
inches 

Number 

of 
irrigations 

Depth  water 

applied, 

inches 

Yield  in 

grain,  pounds 

per  acre 

Cost  of 
irrigation* 

1910,  1911.  1913.  1922 

15.11 

0 

1 
2 
3 

3.0 

5.8 
8.6 

1,548 
2,192 
2,741 

2,893 

$1.70 

3.32 
4.94 

*  Cost  of  irrigation  (water  and  labor)  figured  at  40  cents  per  acre-inch ;  irrigation  furrowing  at  50  cents 
per  acre  per  irrigation. 


Conclusions  on  Irrigation  of  Corn  and  Grain  Sorghum  (at  Davis). 

1.  On  medium  soil  types  and  in  years  of  normal  rainfall  in  the 
Sacramento  Valley,  the  net  irrigation  requirement  for  full  crop  pro- 
duction should  not  exceed  12  acre-inches  per  acre,  applied  in  not 
more  than  three  irrigations. 

2.  In  years  of  deficient  rainfall  the  net  seasonal  irrigation  require- 
ment for  these  crops  should  not  exceed  18  acre-inches,  applied  in  not 
more  than  four  irrigations. 

3.  Irrigation  of  land  before  seeding  is  advisable  when  rainfall 
conditions  have  been  such  that  a  proper  seed  bed  cannot  be  prepared, 
or  where  there  is  not  sufficient  moisture  in  the  surface  soil  to  insure 
a  proper  germination  of  the  seed. 

4.  Under  the  furrow  method  of  irrigation  a  normal  depth  of  irri- 
gation is  4  acre-inches  per  acre  for  each  irrigation. 


12m-3,'28 


